Electronic devices that process private or sensitive information often employ data security operations, such as cryptography, to ensure that critical operations and communications are secure and that the information is not exposed to unauthorized individuals or devices. Implementation of the data security operations, however, is itself subject to security risks. Such security risks are present, for example, in a type of non-invasive attack known as a side channel attack. A typical side channel attack collects various “side channel information” about an electronic device without directly interfering with, or being easily detected by, the device. Differential power analysis (DPA) attack is a type of side channel attack that analyzes power signals collected from a series of cryptographic executions performed by an electronic device. While this “power signal” side channel information is often subtle and difficult to interpret, the information correlates to certain secret information of the device, and an attacker can implement various statistical algorithms to effectively analyze the information and breach the device's security.
In an illustrative scenario of a DPA attack, power consumption curves of a cryptographic operation executed by a particular device are monitored. The power curves represent incremental changes in power over time over different iterations of a cryptographic operation. In particular, the power used by the device during normal operation is compared to power used during the different cryptographic executions. By monitoring these power variations, an attacker can look for statistical differences between particular subsets of the executions; these differences are correlated with particular key bits to identify the cypher key used and/or other sensitive data involved.
Current defenses against DPA attacks focus on techniques that alter the observable power that can be analyzed. Such techniques include, for example, adding random delays, data masking, and noise generation. Other defenses focus on protection of the power system itself, such that any attempt to physically access the power system is not possible without setting off tamper detection. These defenses, however, merely render the DPA more complex, but not impossible, as more complex statistical algorithms and additional measurement samples may be employed to overcome such techniques. Therefore, there is a need for a more effective approach of protecting devices from DPA attacks.